In recent years, in radio communication, particularly in mobile communication, various kinds of information such as images and data other than speech have become targets of transmission. In the future, there will be a growing demand for transmission of various content, and so there will be a growing need for high speed transmission. However, when high speed transmission is performed in mobile communication, the influence of delay waves due to multipath cannot be ignored, and transmission characteristics degrade due to frequency selective fading.
As one of the techniques for combating frequency selective fading, attention is focused on multicarrier communication such as OFDM (Orthogonal Frequency Division Multiplexing). Multicarrier communication transmits data using a plurality of carriers (subcarriers) with the transmission rate lowered to a degree not causing frequency selective fading, and thereby performs high speed transmission. Particularly, in the OFDM scheme, a plurality of subcarriers where data is arranged are orthogonal to each other, and so high frequency efficiency can be achieved among multicarrier communication. Further, the OFDM scheme can be realized using a relatively simple hardware configuration, and so attention is focused on the OFDM scheme particularly, and various study is underway.
In the 3GPP LTE standardization, study is underway to make it possible to use a plurality of radio communication mobile station apparatuses (hereinafter abbreviated as “mobile stations”) with different frequency bandwidths (hereinafter abbreviated as “bandwidths”) in a mobile communication system of the OFDM scheme. Such a mobile communication system is often referred to as a “scalable bandwidth communication system.” For example, in a scalable bandwidth communication system having a frequency band (hereinafter abbreviated as “band”) of 20 MHz, a mobile station capable of communicating at one of 5 MHz, 10 MHz and 20 MHz, can be used. Hereinafter, a mobile station capable of communicating at 5 MHz, a mobile station capable of communicating at 10 MHz and a mobile station capable of communicating at 20 MHz are referred to as a “5 MHz mobile station,” “10 MHz mobile station” and “20 MHz mobile station,” respectively. Further, out of the three types of mobile stations that can be used, a mobile station with the minimum communication capability is referred to as a “minimum capability mobile station.” Therefore, in this case, the 5 MHz mobile station is the minimum capability mobile station. In such a scalable bandwidth communication system, the 5 MHz mobile station is assigned a 5 MHz bandwidth in the 20 MHz band and performs communication. Further, the 20 MHz mobile station can perform communication using the whole of the 20 MHz band and so can perform communication at higher speed.
On the other hand, in a mobile communication system adopting the cellular scheme, a radio communication base station apparatus (hereinafter abbreviated as “base station”) broadcasts per cell, information required for communicating user data, to all the mobile stations in the cell. This broadcast information is transmitted using a BCH (Broadcast CHannel). The BCH is one of common control channels in downlink and transmits broadcast information such as system information, cell information and transmission parameters, and the like. The broadcast information transmitted using the BCH is hereinafter referred to as “BCH data.” Mobile stations receive BCH data upon power activation, learn system information, cell information, transmission parameters, and the like, and then start communicating user data. Further, the transmission parameters such as frame formats are updated over time, and so mobile stations need to receive BCH data even while communicating user data.
As a method for transmitting BCH data in the above-described scalable bandwidth communication system, as shown in the upper part of FIG. 1, transmitting BCH data using the center frequency band (1.25 MHz bandwidth) of 20 MHz band, is proposed (see Non-Patent Document 1). As shown in the upper part of FIG. 1, in this scalable bandwidth communication system, in accordance with a bandwidth (5 MHz) in which the minimum capability mobile station can perform communication, a 20 MHz band is equally divided into four bands FB1 to FB4 per 5 MHz bandwidth. The minimum capability mobile station is assigned one of the bands FB1 to FB4 and communicates user data. Here, one frame is 10 ms and is comprised of 20 subframes. BCH data is transmitted once per one frame using one of the subframes. Further, the content of BCH data is updated in a relatively long cycle of approximately 100 frames. Non-Patent Document 1: 3GPP RAN WG1 Ad Hoc on LTE meeting (2005.06) R1-050590 “Physical Channels and Multiplexing in Evolved UTRA Downlink”